1. Field of the Invention
This invention relates to a silver halide color photographic material containing an improved magenta dye-forming coupler.
2. Description of the Prior Art
It is well known that when silver halide photographic materials are color-developed after light-exposure, couplers contained in the color photographic materials react with the oxidation products of aromatic primary amino developing agents to provide indophenol, indoaniline, indamine, azomethine, phenoxazine, phenazine, and other similar dyes, whereby color images are formed. In such a known system, color reproduction is conducted by a subtractive color process and yellow, magenta, and cyan dye images corresponding to blue, green, and red light images, respectively, are formed. In general, an acylacetamide coupler or a dibenzoylmethane coupler is used for forming yellow dye images, a pyrazolone coupler, a cyanoacetyl coupler or an indazolone coupler is used for forming magenta dye images, and a phenolic coupler such as a phenol and a naphthol is used for forming cyan dye images.
Various 5-pyrazolone derivatives are known for forming magenta dye images for trichromatic color photography. For instance, as the substituents at the 3-position of the 5-pyrazolone ring, an alkyl group and an aryl group are known. Furthermore, as such substituents, alkoxyl groups as described in the specification of U.S. Pat. No. 2,439,098, acylamino groups as described in the specifications of U.S. Pat. Nos. 2,369,489 and 2,600,788 and ureido groups as described in the specification of U.S. Pat. No. 3,558,319 are known. Other examples of such substituent are anilino groups. For instance, 3-anilino-5-pyrazolone couplers are described in the specification of U.S. Pat. No. 2,311,081 (or Reissue No. 22,329) and also many improvements in such couplers have been proposed. As an example British Pat. No. 956,261 teaches that an azomethine dye obtained from a 3-anilino-5-pyrazolone derivative having an alkoxyl group or a halogen atom, as a substituent, at the ortho-position of the anilino group has particularly less unnecessary absorption in a red light region, which is a preferred spectral characteristic for color photography. As an example of non-diffusible couplers which belong to this type of coupler and which can be incorporated in photographic emulsions, the 3-(acylaminoanilino)-5-pyrazolones represented by the following general formula (M) are known: ##SPC1##
Wherein D.sub.1 represents an aryl group, D.sub.2 CO- represents an acyl group, D.sub.3 represents a hydrogen atom or a residue such as a phenoxy group which is released by the oxidation product of an aromatic primary amino developing agent, and L represents a chlorine atom or a methoxy group.
These couplers must be provided with diffusion resistance in order that these coupler are prevented from diffusing into other photographic emulsion layers having different spectral sensitivities and mixing with other couplers to reduce the color reproduction of the photographic emulsion layers by causing color mixing when these couplers are used in silver halide photographic emulsion layers of color photographic materials. For this purpose the introduction into the coupler molecule of a hydrophobic residue having more than 8 carbon atoms, which contributes to reducing the diffusibility of the coupler, as a ballasting group, is required.
To incorporate such non-diffusible couplers into photographic emulsions, the following three methods have generally been employed:
1. Aqueous solution system: The non-diffusible coupler having a water-solubilizing group such as a carboxyl group or a sulfo group and being soluble in an alkaline aqueous medium is incorporated in a photographic emulsion in the form of a neutral or alkaline aqueous solution thereof and then the emulsion is neutralized with an acid.
2. Oil solution system: The non-diffusible coupler is dissolved in an organic solvent, the solution is dispersed in an aqueous medium as fine colloidal particles, and the dispersion is added to a photographic emulsion.
3. The non-diffusible coupler is melted by heating and the molten coupler is directly dispersed in a photographic emulsion or aqueous medium.
Of these systems, the present invention is concerned with the aforesaid oil solution system (2). In order to form a green-sensitive photographic emulsion layer having excellent properties using a coupler forming magenta dye images employing the oil solution system, the coupler must satisfy the following conditions: that is to say, the coupler must have high coupling reactivity with the oxidation product of a developing agent, the magenta dye image formed by color development must have light absorption characteristics appropriate for the color reproduction principle of the trichromatic subtraction color process, the magenta dye image formed must have a high fastness so that the image can be stored under severe conditions without fading, the coupler must not adversely influence the properties of photographic emulsions, and further the coupler must be readily soluble in an organic solvent employed for dispersing the coupler in a photographic emulsion and be less crystallized in the solvent.
On the other hand, since conventionally known magenta dye-forming couplers in the oil solution system show insufficient reactivity with the oxidation product of developing agent in the dispersed state in photographic emulsion layers, it is difficult to obtain green sensitive emulsion layers having excellent photographic properties using the oil solution system.
Because a magenta dye image in a color photograph using the trichromatic subtraction color process absorbs light in the longest wave-length region of human visible sensitivity, the light absorption characteristics of the magenta dye image are a very important factor in determining the color reproduction properties of the color photograph. In particular, it has been believed that the improvement in the sharpness of spectral absorption curve and the reduction in the second absorption specific to pyrazolone magenta coupler give better absorption characteristics for the magenta dye image and various efforts have been made in this respect.
Also, when conventional magenta dye images formed from various magenta dye image-forming couplers are stored under high temperature and humidity conditions for a long period of time, they tend to fade and to prevent the occurence of such a tendency in the case of using conventional magenta dye-forming couplers, it is inevitable that formaldehyde be used in the course of development.